This invention relates generally to missile guidance systems and more particularly to radar guided missile systems.
As is known in the art, a missile may be guided to a target by guidance signals developed from tracking data obtained either at a surface-based radar station or by radar means located totally, or partially, within the missile. The former system is commonly referred to as a command guidance system and the latter as a missile homing guidance system. For example, in a command guidance system where a missile is used to intercept an airborne target, a large, remotely located, high resolution surface-based radar system and high speed digital computer are provided for selecting one of a plurality of targets, tracking both the missile and the selected target, calculating proper guidance signals for the missile from the generated tracking data, and transmitting such signals to the missile to enable the missile to intercept the target. As is known, a reference element, such as an attitude stabilized platform is generally required to be contained within the missile for transformation of the transmitted signals into missile control signals.
In a missile homing guidance system, a smaller, light weight, lower power target tracking radar system may be provided for generation of both target tracking data and guidance signals. In one type of missile homing guidance system, both the radar transmitter and receiver are located in the missile and in another type of homing system the radar transmitter is located remotely from the missile while the receiver is located in the missile. The former missile homing system is referred to as an active guidance system and the latter as a semi-active guidance system. Generally, such semi-active guidance system includes a target tracking radar antenna gimballed within the missile and coupled to a control system (i.e., the antenna and control system therefore being referred to collectively as a missile seeker) for tracking the target and to thereby generate guidance signals for the missile.
In one type of missile system, the features of command guidance and semi-active guidance techniques are combined. During the early portion of the missile's flight, the missile is guided by a command guidance phase where the guidance command signals are developed by the digital computer operated in response to signals obtained by tracking both the missile and a selected target with a remote, high resolution, surface-based radar system. During the later portion of the flight, the missile is guided by a semi-active guidance phase where guidance signals are obtained by tracking the target with the missile-borne radar receiver fed by the gimballed antenna system which receives reflected power from target illuminations by the surface-based radar system. In one system, the antenna provides a stable reference for the command guidance phase, such system being described in U.S. Pat. No. 4,142,695 entitled "Vehicle Guidance System" issued Mar. 6, 1979 and assigned to the same assignee as the present invention.
As is also known in the art, the use of an initial command guidance system phase followed by an active, missile homing guidance system terminal phase has been suggested. In such suggested arrangement, after the initial command guidance system phase (i.e., at the commencement of the active terminal phase), the missile seeker would first go through a search phase to search for the target and then, once the target is acquired, the missile seeker would go into a target tracking mode to thereby guide the missile to the target. With small targets, the search phase may be relatively long thereby reducing the time to guide the missile to the target. Generally, however, the shorter the time the missile has to guide to the target, the less likelihood the missile will successfully intercept the target.